An improvement of the structure of venetian blind to fix a fixing rail and two fixing plates on the bottom side and the top side of the frame of the window and then combine a plurality of supporting seats equally spaced inside the fixing rail and connect the supporting seats in series with a regulating shaft which is combined with a regulating wheel; the supporting seats and the lower end of the slat are combined together with the top end of the slat to be restricted and positioned by two fixing plates. The assembly is driven by the regulating wheel to adjust the angle of the slats and provide consumers with the convenience of easy assembly.